Meal Timing Regulates the Human Circadian System.
Level 3 - non-randomized controlled study
Non-randomized within-subject sequential laboratory study
PubMed 28578930 · doi:10.1016/j.cub.2017.04.059
What was done
Ten healthy young men participated in a 13-day laboratory study assessing the effects of a 5-hour meal delay on central and peripheral circadian rhythms. Three meals were given at 5-hour intervals, starting either 0.5 hours (early) or 5.5 hours (late) after waking. Participants acclimated to early meals and then switched to late meals for 6 days. Circadian rhythms were assessed after each meal schedule using a 37-hour constant routine protocol with continuous wakefulness, constant environmental conditions, and hourly isocaloric snacks. Measured outcomes included actigraphic sleep parameters, subjective hunger and sleepiness, plasma melatonin, cortisol, triglycerides, glucose, whole-blood clock gene expression, and adipose tissue PER2 mRNA expression.
What was found
Meal timing did not alter actigraphic sleep parameters or constant-routine rhythms of subjective hunger, sleepiness, master clock markers (plasma melatonin and cortisol), plasma triglycerides, or whole-blood clock gene expression. Late meals delayed plasma glucose rhythms by 5.69 ± 1.29 hours (p < 0.001) and reduced average glucose concentrations by 0.27 ± 0.05 mM (p < 0.001). Adipose tissue PER2 mRNA rhythms were delayed by 0.97 ± 0.29 hours (p < 0.01).
Why it matters
These findings demonstrate that meal timing can entrain specific peripheral circadian clocks and glucose rhythms in humans independently of the central suprachiasmatic nucleus pacemaker.
Limits
The study was conducted in a very small sample (n = 10) restricted to healthy young men. The trial was sequential rather than randomized crossover, creating potential order effects, and findings from strict constant routine laboratory conditions may differ from normal daily life.
Cited by
- supports Circadian rhythms in humans are regulated not only by light exposure but also by the timing of food intake.